Valve seat installation specifications?

[bruce_launceston]

I have just had a new exhaust valve seat fail and 'drop', ie: it came loose and moved 3 or 4mm into the combustion chamber.
Luckily there appears to be no lasting damage.
The machine shop that installed the new exhaust valves, guides and seats will reinstall another set of seats but their machine is preset with a defined amount of 'interference'.
This can be overriden and I was hoping to find the factory specs for how many thou' (or mm) interference there should be.

Do any of you knowledgable gentlemen have this information?

Cheers Bruce

[Barry]

Bruce

Duane Ausherman has some info here although there is a gap when he gets to R65's. Still the figures from other models should give you an idea. Interesting to see only small differences from the earlier models to the later. Best guess looks like roughly 0.6 to 0.8 of a thou for ours.

http://w6rec.com/duane/bmw/engine.htm

[bruce_launceston]

Thanks Barry, that seems to be the same information that was reproduced on another website.
There wasn't any acknowledgement of the original source on the other one so I was looking for confirmation.

I have some pages from a genuine BMW factory manual where it gives the seat sizes and angles but not the interference.

Cheers

[nhmaf]

I *thought* that I had that information around here somewhere but cannot find it - will search some more and post again if I find it-sorry!

[bruce_launceston]

The later BMW manuals specify the seat diameter and the seat bore diameter.
A process of basic maths shows that the interference is 0.20mm (.0079").

They used to give a line in the manual called 'interference fit in cylinder head' and specify this number and I was still looking for this line even though the information was there all the time.

Thanks and cheers.

Hope to have the BM back on the road soon, I'm slumming around on a Ducati SuperSport in the meantime lol.

[montmil]

...Hope to have the BM back on the road soon, I'm slumming around on a Ducati SuperSport...

Poor Bruce. The things he must endure.

Monte

[bruce_launceston]

I picked up my heads after work tonight and reinstalled the barrels, heads, rocker gear, exhausts and carbs. I bought another full top end gasket set so I installed the new pushrod tube rubbers, base o-rings and head gaskets even though the ones I took off only had 100 km on them.

I also installed new rings along with the new exhaust valves, seats and guides. The original exhaust valve seats were receding and the guides were quite worn, the inlet valves were fine.

The shop removed the loose valve seat from the left head and also the one from the right head and reinstalled oversize ones with a 0.008" interference fit, I will have to trust that these will not come loose.

After 3 1/2 hours of careful work it started easily and sounded fine. I only ran it for a minute as it's dark and raining so I will test ride it to work tomorrow morning.

Now that the BM is back on the road I can fix the little things that have appeared on the Ducati after 3 weeks of use, new fork seals, sticking rear brake, not charging ....